System and method for catheter-based plasma coagulation

ABSTRACT

A plasma instrument includes an elongated body defining a lumen therethrough, the lumen being in fluid communication with an ionizable media source; and a plasma applicator coupled to a distal portion of the elongated body. The plasma applicator includes: an active electrode configured to couple to an active terminal of a generator; and a corona electrode configured to couple to a return terminal of a generator. The plasma instrument also includes a switching element coupled to the corona electrode, the switching element configured to control at least one of resistivity or connectivity of the corona electrode to a generator.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the benefit of and priority to U.S.Provisional Application Ser. No. 62/370,035, filed on Aug. 2, 2016, theentire contents of which are incorporated herein by reference.

BACKGROUND Technical Field

The present disclosure relates to plasma devices and systems for surfaceprocessing and tissue treatment. More particularly, the disclosurerelates to a monopolar coagulation handpiece for generating chemicallyreactive, plasma-generated species.

Background of Related Art

Electrical discharges in dense media, such as liquids and gases at ornear atmospheric pressure, can, under appropriate conditions, result inplasma formation. Plasmas have the unique ability to create largeamounts of chemical species, such as ions, radicals, electrons,excited-state (e.g., metastable) species, molecular fragments, photons,and the like. The plasma species may be generated in a variety ofinternal energy states or external kinetic energy distributions bytailoring the plasma electron temperature and the electron density. Inaddition, adjusting spatial, temporal, and temperature properties of theplasma creates specific changes to the material being irradiated by theplasma species and associated photon fluxes. Plasmas are also capable ofgenerating photons that have sufficient energy to initiate photochemicaland photocatalytic reaction paths in biological and other materials thatare irradiated by the plasma photons.

Although plasma-based devices to treat tissue are known, conventionalplasma-based devices are not well suited for accurately controlling theeffects on tissue, such as desiccation depth. This is of particularimportance in surgical procedures where controlling the depth of theplasma penetration is key to achieving a desired therapeutic effect,such as in plasma treatment of ulcerative colitis, which is a disease ofthe inner lining (mucosa) of the colon. Ulcerative colitis ischaracterized by inflammation of the mucosa layer, which causes theformation of ulcers. This can in turn, cause protrusion of the colonwalls into digestive pathways and may become cancerous if leftuntreated. Thus, the goal of plasma-based ulcerative colitis treatmentsis to treat the mucosa without damaging the underlying muscle layers.Accordingly, there is a need for a plasma treatment system and apparatusfor generating plasma effluent that is capable of treating tissue to adesired depth.

SUMMARY

Plasmas have broad applicability and provide alternative solutions toindustrial, scientific and medical needs, especially workpiece (e.g,tissue) surface treatment at any temperature range. Plasmas may bedelivered to the workpiece, thereby affecting multiple changes in theproperties of materials upon which the plasmas impinge. Plasmas have theunique ability to create large fluxes of radiation (e.g., ultraviolet),ions, photons, electrons and other excited-state (e.g., metastable)species which are suitable for performing material property changes withhigh spatial, material selectivity, and temporal control. Plasmas mayalso remove a distinct upper layer of a workpiece with little or noeffect on a separate underlayer of the workpiece or it may be used toselectively remove a particular tissue from a mixed tissue region orselectively remove a tissue with minimal effect to adjacent organs ofdifferent tissue type.

The plasma species are capable of modifying the chemical nature oftissue surfaces by breaking chemical bonds, substituting or replacingsurface-terminating species (e.g., surface functionalization) throughvolatilization, gasification, or dissolution of surface materials (e.g.,etching). With proper techniques, material choices, and conditions, onecan remove one type of tissue entirely without affecting a nearbydifferent type of tissue. Controlling plasma conditions and parameters(including S-parameters, V, I, Θ, and the like) allows for the selectionof a set of specific particles, which, in turn, allows for selection ofchemical pathways for material removal or modification as well asselectivity of removal of desired tissue type.

According to one embodiment of the present disclosure, a plasmainstrument is disclosed. The plasma instrument includes an elongatedbody defining a lumen therethrough, the lumen being in fluidcommunication with an ionizable media source; and a plasma applicatorcoupled to a distal portion of the elongated body. The plasma applicatorincludes: an active electrode configured to couple to an active terminalof a generator; and a corona electrode configured to couple to a returnterminal of a generator. The plasma instrument also includes a switchingelement coupled to the corona electrode, the switching elementconfigured to control at least one of resistivity or connectivity of thecorona electrode to a generator.

According to one aspect of the above embodiment, the plasma instrumentfurther includes a proximity sensor configured to measure a distancebetween the plasma applicator and tissue.

According to one aspect of the above embodiment, the plasma instrumentfurther includes an atmospheric sensor configured to measure a propertyof air surrounding the plasma applicator.

According to one aspect of the above embodiment, the plasma applicatorfurther includes a nozzle coupled to a distal portion of the coronaelectrode.

According to one aspect of the above embodiment, the active electrodeextends through the corona electrode and at least partially through thenozzle.

According to one aspect of the above embodiment, the elongated body isflexible.

According to another embodiment of the present disclosure, a plasmasystem is disclosed. The plasma system includes: a generator having anactive terminal and a return terminal; an ionizable media source; and aplasma instrument, which includes an elongated body defining a lumentherethrough, the lumen being in fluid communication with the ionizablemedia source; and a plasma applicator coupled to a distal portion of theelongated body. The plasma applicator includes: an active electrodecoupled to the active terminal of the generator; and a corona electrodecoupled to the return terminal of the generator. The plasma instrumentalso includes a switching element coupled to the corona electrode, theswitching element configured to control at least one of resistivity orconnectivity of the corona electrode to the generator.

According to one aspect of the above embodiment, the plasma systemfurther includes a return electrode pad coupled to the return terminal.

According to one aspect of the above embodiment, the plasma systemfurther includes a first return lead coupled to the corona electrode; asecond return lead coupled to the return electrode pad; and a commonreturn lead coupled to the first and second return leads, the commonreturn lead being coupled to the return terminal.

According to one aspect of the above embodiment, the plasma instrumentfurther includes a proximity sensor configured to measure a distancebetween the plasma applicator and tissue.

According to one aspect of the above embodiment, the generator includesa controller coupled to the proximity sensor, the controller configuredto control at least one of energy output of the generator or a state ofthe switching element based on the distance.

According to one aspect of the above embodiment, the plasma instrumentfurther includes an atmospheric sensor configured to measure an airproperty surrounding the plasma applicator.

According to one aspect of the above embodiment, the generator includesa controller coupled to the atmospheric sensor, the controllerconfigured to control at least one of energy output of the generator ora state of the switching element based on the air property.

According to one aspect of the above embodiment, the air property isselected from the group consisting of humidity and oxygen saturation.

According to one aspect of the above embodiment, the plasma applicatorfurther includes a nozzle coupled to a distal portion of the coronaelectrode. The active electrode extends through the corona electrode andat least partially through the nozzle.

According to one aspect of the above embodiment, the elongated body isflexible.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of thedisclosure and, together with a general description of the disclosuregiven above, and the detailed description of the embodiments givenbelow, serve to explain the principles of the disclosure, wherein:

FIG. 1 is a diagram of a plasma system according to the presentdisclosure;

FIG. 2 is a perspective view of a plasma instrument of the system ofFIG. 1;

FIG. 3 is a perspective view of an electrode assembly of the plasmainstrument of FIG. 2;

FIG. 4 is a perspective, cross-sectional view of the electrode assemblyof FIG. 4 taken along a cross-sectional line 4-4;

FIG. 5 is a schematic, block diagram of the plasma system of FIG. 1according to the present disclosure; and

FIG. 6 is a flow chart of a method for generating plasma using theplasma system of FIG. 1.

DETAILED DESCRIPTION

Plasmas may be generated using electrical energy that is delivered aseither direct current (DC) electricity or alternating current (AC)electricity at frequencies from about 0.1 hertz (Hz) to about 100gigahertz (GHz), including radio frequency (“RF”, from about 0.1 MHz toabout 100 MHz) and microwave (“MW”, from about 0.1 GHz to about 100 GHz)bands, using appropriate generators, electrodes, and antennas. Choice ofexcitation frequency, the workpiece, as well as the electrical circuitsthat are used to deliver electrical energy to the workpiece affect manyproperties of the plasma. The performance of the plasma chemicalgeneration, the delivery system and the design of the electricalexcitation circuitry are interrelated. Specifically, the choices ofoperating voltage, frequency, and current levels (as well as phase)affect the electron temperature and electron density. Further, choicesof electrical excitation and plasma device hardware also determine how agiven plasma system responds dynamically to the introduction of newingredients to the host plasma gas or liquid media.

Plasma effluent may be used to coagulate, cauterize, or otherwise treattissue through direct application of high-energy plasma. In particular,kinetic energy transfer from the plasma to the tissue causes healing,and thus, provides for thermal coagulation of bleeding tissue. Plasmabeam coagulation utilizes a handheld electrosurgical instrument havingone or more electrodes that are energizable by an electrosurgicalgenerator, which outputs a high-intensity electric field suitable forforming plasma using ionizable media (e.g., inert gas).

Briefly, the present disclosure provides an electrosurgical systemincluding a generator configured to generate energy that is transmittedto a plasma instrument, which is also coupled to a source of anionizable medium. The excitation waveform generated by the generatorignites the ionizable medium flowing through the plasma device, therebyforming a plasma effluent. The electrosurgical system according to thepresent disclosure includes various sensors, such as an atmosphericsensor and a proximity sensor, which provide measurement signals used bythe generator for igniting and maintaining the plasma effluent. Inaddition, the plasma instrument also includes a corona electrode thataides in ignition and formation of the plasma effluent.

Referring initially to FIG. 1, a plasma system 10 is disclosed. Thesystem 10 includes a plasma instrument 12 that is coupled to a generator14, an ionizable media source 16 which may also include an optionalprecursor source (not shown). Generator 14 includes any suitablecomponents for delivering power to the plasma instrument 12. Moreparticularly, the generator 14 may be any radio frequency generator orother suitable power source capable of generating electrical powersufficient to ignite the ionizable media to generate plasma. Generator14 may be an electrosurgical generator that is adapted to supply theinstrument 12 with electrical power at a frequency from about 100 kHz toabout 4 MHz, in embodiments the frequency may range from about 200 kHzto about 3 MHz, and in further embodiments the frequency may range fromabout 300 kHz to about 1 MHz.

In embodiments, electrosurgical energy is supplied to the instrument 12by the generator 14 via an instrument cable 4. The cable 4 includes asupply lead 6 connecting the instrument 12 to an active terminal 230(FIG. 5) of the generator 14 and a first return lead 8 a connecting theinstrument 12 to a return terminal 232 (FIG. 5) of the generator 14. Itis envisioned that the plasma instrument 12 may be utilized as anelectrosurgical pencil for application of plasma to tissue.

The system 10 also includes one or more return electrode pads 18 that,in use, are disposed on a patient to minimize the chances of tissuedamage by maximizing the overall contact area with the patient. Theenergy is returned to the generator 14 through the return electrode pad18 via a second return lead 8 b to the return terminal 232 (FIG. 5) ofthe generator 14. Return leads 8 a and 8 b are coupled to a commonreturn lead 8, which is in turn, connected to the return terminal 232(FIG. 5).

The plasma instrument 12 is shown as a catheter having a handle 20 and aflexible elongate body 22 having a proximal portion 24 coupled to thehandle 20 and a distal portion 26. The elongate body 20 may be tubularand may be formed from any suitable flexible dielectric material, suchas polyimide. The handle 20 also includes an articulation mechanism 28having a wire 29, which extends the length of the elongate body 20. Thewire 29 may be wound or unwound by the articulation mechanism 26 toarticulate the distal portion 26 of the elongate body 20.

With continued reference to FIG. 1, the ionizable media source 16 may becoupled to the plasma instrument 12 via tubing 15. The tubing 15 may befed from multiple sources of ionizable media and/or precursorfeedstocks, which may be combined into unified tubing to deliver amixture of the ionizable media and the precursor feedstock to theinstrument 12 at a proximal end thereof. This allows for the plasmafeedstocks, e.g., the precursor feedstock and the ionizable gas, to bedelivered to the plasma instrument 12 simultaneously prior to ignitionof the mixture therein.

The ionizable media source 16 may include various flow sensors andcontrollers (e.g., valves, mass flow controllers, etc.) to control theflow of ionizable media to the instrument 12. During operation, theionizable media and/or the precursor feedstock are provided to theplasma instrument 12 where the plasma feedstocks are ignited to formplasma effluent containing ions, radicals, and/or photons from thespecific excited species and metastables that carry internal energy todrive desired chemical reactions in the workpiece or at the surfacethereof. The feedstocks may be mixed upstream from the ignition point ormidstream (e.g., at the ignition point) of the plasma effluent.

The ionizable media source 16 may include a storage tank, a pump, and/orflow meter (not explicitly shown). The ionizable media may be a liquidor a gas such as argon, helium, neon, krypton, xenon, radon, carbondioxide, nitrogen, hydrogen, oxygen, etc. their mixtures, and the like.These and other gases may be initially in a liquid form that is gasifiedduring application. The precursor feedstock may be either in solid,gaseous or liquid form and may be mixed with the ionizable media in anystate, such as solid, liquid (e.g., particulates or droplets), gas, andcombinations thereof.

In another embodiment, the ionizable media and precursor feedstocks maybe supplied at separate connections, such that the mixing of thefeedstocks occurs within the plasma instrument 12 upstream from theignition point. In this manner, the plasma feedstocks are mixedproximally of the ignition point.

In a further embodiment, the plasma feedstocks may be mixed midstream,e.g., at the ignition point or downstream of the plasma effluent,directly into the plasma. It is also envisioned that the ionizable mediamay be supplied to the instrument 12 proximally of the ignition point,while the precursor feedstocks are mixed therewith at the ignitionpoint. In a further illustrative embodiment, the ionizable media may beignited in an unmixed state and the precursors may be mixed directlyinto the ignited plasma. Prior to mixing, the plasma feedstocks may beignited individually. The plasma feedstock may be supplied at apredetermined pressure to create a flow of the medium through theinstrument 12, which aids in the reaction of the plasma feedstocks andproduces a plasma effluent. The plasma according to the presentdisclosure may be generated at or near atmospheric pressure under normalatmospheric conditions.

In one embodiment, the precursors may be any chemical species capable offorming reactive species such as ions, electrons, excited-state (e.g.,metastable) species, molecular fragments (e.g., radicals), and the like,when ignited by electrical energy from the generator 14 or whenundergoing collisions with particles (electrons, photons, or otherenergy-bearing species of limited and selective chemical reactivity)formed from the ionizable media 16. More specifically, the precursorsmay include various reactive functional groups, such as acyl halide,alcohol, aldehyde, alkane, alkene, amide, amine, butyl, carboxylic,cyanate, isocyanate, ester, ether, ethyl, halide, haloalkane, hydroxyl,ketone, methyl, nitrate, nitro, nitrile, nitrite, nitroso, peroxide,hydroperoxide, oxygen, hydrogen, nitrogen, and combinations thereof. Inembodiments, the precursor feedstocks may be water, halogenoalkanes,such as dichloromethane, tricholoromethane, carbon tetrachloride,difluoromethane, trifluoromethane, carbon tetrafluoride, and the like;peroxides, such as hydrogen peroxide, acetone peroxide, benzoylperoxide, and the like; alcohols, such as methanol, ethanol,isopropanol, ethylene glycol, propylene glycol, alkalines such as NaOH,KOH, amines, alkyls, alkenes, and the like. Such precursor feedstocksmay be applied in substantially pure, mixed, or soluble form.

With reference to FIG. 2-4, the distal portion 26 of the elongate body20 is coupled to a plasma applicator 30, which includes an activeelectrode assembly 32. The active electrode assembly 32 includes anactive electrode 40 (FIG. 3) having a proximal portion 42 and a distalportion 43 (FIG. 4). The proximal portion 42 is enclosed in a conductivecollar 44, which is coupled to the supply lead 6. The supply lead 6 iselectrically coupled to an outer surface of the conductive collar 44such that the supply lead 6 is disposed outside the gas flow within theelongate body 20. In embodiments, the supply lead 6 may be enclosed inan insulative sheath and be disposed within the elongate body 20. Infurther embodiments, the supply lead 6 may be disposed within the tubingof the elongate body 20, e.g., during the extrusion process. In yetanother embodiment, the supply lead 6 may be coupled directly to theactive electrode 40.

The conductive collar 44 has a substantially tubular shape defining alumen 46 (FIG. 4) therethrough. The distal portion 26 of the elongatebody 20 may be stretched over a distal portion of the conductive collar44 to create a gas tight seal. The conductive collar 44 may also includeone or more slots 44 a and 44 b configured to couple to extensions 40 aand 40 b of the active electrode 40 to provide for an electrical andmechanical coupling therebetween. This connection also aligns the activeelectrode 40 within the conductive collar 44.

The active electrode 40 may have any suitable shape that does notobstruct the lumen 46, ensuring that ionizable medium may flow throughthe lumen 46. In embodiments, the active electrode 40 may have a taperedconfiguration in which the proximal portion 42 is wider than the distalportion 43 such that the change in width of the active electrode 40 isgradual from the proximal portion 42 to the distal portion 43.

The distal portion 43 of the active electrode 40 is enclosed in a coronaelectrode 48, which is coupled to the return lead 8 a. The return lead 8a may be coupled to the corona electrode 48 (FIG. 2) in any suitablemanner as described above with respect to coupling the supply lead 6 tothe conductive collar 44. Similarly to the conductive collar 44, thecorona electrode 48 may also have a substantially tubular shape defininga lumen (not shown) therethrough. The plasma applicator 30 also includesa nozzle 52 coupled to a distal end of corona electrode 48. The nozzle52 also defines a lumen 54, in which the distal portion 43 of the activeelectrode 40 is disposed.

The active electrode 40, the conductive collar 44, and the coronaelectrode 48 may be formed from any suitable conductive materialincluding metals, such as stainless steel, copper, aluminium, tungsten,and combinations and alloys thereof. The nozzle 52 may be formed fromany suitable dielectric material including thermoplastic materials ifthe temperature of the plasma is sufficiently low or any other suitableheat-resistant dielectric material, including ceramic materials.

In embodiments, the plasma applicator 30 may also include a proximitysensor 60 (FIG. 2). The proximity sensor 60 is used to measure thedistance between the tissue and the nozzle 52. The measured distance isused by the generator 14 to control energy and thereby maintain theplasma. The proximity sensor 60 may be an electromagnetic sensorconfigured to emit an electromagnetic field or a beam of electromagneticradiation (e.g., visible light, infrared, etc.), and measure changes inthe field or beam. In embodiments, the proximity sensor 60 may be acapacitive sensor configured to detect distance to tissue based on thedielectric properties thereof.

The plasma applicator 30 may also include an atmospheric sensor 62, suchas a humistor, configured to sense relative humidity in and around thesurgical site. In embodiments, the atmospheric sensor 62 may be alsoinclude an oxygen sensor configured to measure concentration of oxygenin the surrounding atmosphere.

FIG. 5 shows a schematic block diagram of the generator 14 configured tooutput electrosurgical energy. The generator 14 includes a controller224, a power supply 227, and a radio-frequency (RF) amplifier 228. Thepower supply 227 may be a high voltage, DC power supply connected to anAC source (e.g., line voltage), provides high voltage, DC power to theRF amplifier 228, which then converts the high voltage, DC power into ACenergy (e.g., electrosurgical or microwave) suitable to ignite theionizable media, and delivers the energy to the active terminal 230. Theenergy is returned thereto via the return terminal 232. The active andreturn terminals 230 and 232 are coupled to the RF amplifier 228 throughan isolation transformer 229. The RF amplifier 228 is configured tooperate in a plurality of modes, during which the generator 14 outputscorresponding waveforms having specific duty cycles, peak voltages,crest factors, etc. It is envisioned that in other embodiments, thegenerator 14 may be based on other types of suitable power supplytopologies.

The controller 224 includes a processor 225 operably connected to amemory 226, which may include transitory type memory (e.g., RAM) and/ornon-transitory type memory (e.g., flash media, disk media, etc.). Theprocessor 225 includes an output port that is operably connected to thepower supply 227 and/or RF amplifier 228 allowing the processor 225 tocontrol the output of the generator 14 according to either open and/orclosed control loop schemes. A closed loop control scheme is a feedbackcontrol loop, in which a plurality of sensors measure a variety oftissue and energy properties (e.g., tissue impedance, tissuetemperature, output power, current, and/or voltage, etc.), and providefeedback to the controller 224. The controller 224 then signals thepower supply 227 and/or RF amplifier 228, which adjusts the DC and/orpower supply, respectively. Those skilled in the art will appreciatethat the processor 225 may be substituted by using any logic processor(e.g., control circuit) adapted to perform the calculations and/or setof instructions described herein including, but not limited to, fieldprogrammable gate array, digital signal processor, and combinationsthereof.

The generator 14 according to the present disclosure includes aplurality of sensors 280, e.g., an RF current sensor 280 a, and an RFvoltage sensor 280 b. Various components of the generator 14, namely,the RF amplifier 228, and the RF current and voltage sensors 280 a and280 b, may be disposed on a printed circuit board (PCB). The RF currentsensor 280 a is coupled to the active terminal 230 and providesmeasurements of the RF current supplied by the RF amplifier 228. Inembodiments the RF current sensor 280 a may be coupled to the returnterminal 232. The RF voltage sensor 280 b is coupled to the active andreturn terminals 230 and 232 provides measurements of the RF voltagesupplied by the RF amplifier 228. In embodiments, the RF current andvoltage sensors 280 a and 280 b may be coupled to active and returnleads 228 a and 228 b, which interconnect the active and returnterminals 230 and 232 to the RF amplifier 228, respectively.

The RF current and voltage sensors 280 a and 280 b provide the sensed RFvoltage and current signals, respectively, to the controller 224, whichthen may adjust output of the power supply 227 and/or the RF amplifier228 in response to the sensed RF voltage and current signals. Thecontroller 224 also receives input signals from the input controls ofthe generator 14 and/or the plasma instrument 12. The controller 224utilizes the input signals to adjust the power output of the generator14 and/or performs other control functions thereon.

The controller 224 is also coupled to the proximity sensor 60 and theatmospheric sensor 62 (FIG. 2). The controller 224 operates thegenerator 14 based on the sensor signals from the proximity sensor 60and the atmospheric sensor 62. In embodiments, the controller 224 mayalso be configured to control the ionizable media source 16 (FIG. 1),such as the flow rate of the ionizable media, based on the sensorreadings.

With continued reference to FIG. 5, the controller 224 is alsoconfigured to control the output of the generator 14 to ensure properignition of the plasma effluent. In that respect, the generator 14includes a switching element 9 coupled to the first return lead 8 a. Theswitching element 9 controls the degree of coupling of the coronaelectrode 48 to the generator 14.

The switching element 9 may be a resistor, a variable resistor, a switchor combinations of these components. In embodiments, the switchingelement 9 may be coupled to the return lead 8 in parallel such that theswitching element 9 may be switched in and out of the combined circuit.The switch state and/or the resistance of the switching element 9 may becontrolled by the controller 224. The resistance provided by theswitching element 9 is used to control the amount of power delivered tothe corona electrode 48. In particular, where the switching element 9 isa variable resistor the resistance may be lowered to ensure that most ofthe power is delivered to the surgical site through the active electrode40 and the corona electrode 48 to commence plasma generation. After theplasma has been ignited, the controller 224 may then increase resistanceof the switching element 9 to a level higher than the starting level tomaintain plasma.

In embodiments where the switching element 9 is a switchable resistor,to commence plasma generation the switching element 9 may be initiallydisconnected from the combined return lead 8 by the controller 224. Oncethe plasma has commenced, the switching element 9 may then be switchedon to maintain plasma generation.

In another embodiment, the switching element 9 may be a switch, suchthat after the plasma is started, the controller 224 disconnects thecorona electrode 48 by deactivating the switch. In further embodiments,the plasma applicator 30 may include a plurality of corona assemblies 48each of which is coupled to the generator 14 by the return lead 8 ahaving the switching element 9. In this configuration, the controller224 controls each of the corona assemblies 48 in the manner describedabove.

In other words, when the corona electrode 48 is coupled to the commonreturn lead 8 due to the switching element 9 being activated or theresistance of the switching element 9 being lowered, the power is splitbetween the corona electrode 48 and the return electrode pad 18. Whenthe corona electrode 48 is disconnected from the common return lead 8due to the switching element 9 being deactivated or the resistance ofthe switching element 9 being increased, the power is returned mostlythrough the return electrode pad 18. With respect to the switchingelement 9 being a variable resistor, the effect of the corona electrode48 on plasma generation may be varied based on a desired effect.

As noted above, the controller 224 is also coupled to the proximitysensor 60 and the atmospheric sensor 62. The sensor data from theproximity sensor 60 and the atmospheric sensor 62 is used by thecontroller 224 to control the plasma ignition process, and inparticular, the coupling of the corona electrode 48 to the generator 14.The proximity sensor 60 provides information regarding the distanceseparating the plasma applicator 30 from tissue. The controller 224utilizes the distance information from the proximity sensor 60 indetermining whether energy from the generator 14 may be supplied to theplasma applicator 30 to commence treatment. If the proximity sensor 60detects that the applicator 30 is contacting tissue, then the controller224 prevents application of energy. In embodiments, the controller 224is also configured to control energy output based on the measureddistance, such as increasing energy as the distance between theapplicator 30 and the tissue increases and decreasing energy as thedistance decreases.

The atmospheric sensor 62 provides data to the controller 224 regardingthe atmosphere surrounding the plasma applicator 30, the data includingoxygen saturation, pressure, relative humidity, and the like. Thecontroller 224 utilizes this data in controlling energy delivered to theplasma applicator 30. Humidity and density of the atmosphere, e.g.,oxygen saturation, play an important role in the effectiveness of theplasma. Decreased oxygen saturation and increased humidity adverselyaffect plasma performance, and therefore, the controller 224 adjusts theoutput of the generator 14 such that the energy supplied by thegenerator 14 compensates for any adverse atmospheric effects as measuredby the atmospheric sensor 62.

With reference to FIG. 6, a method for operating the system 10 accordingto the present disclosure, initially includes measuring the distance andatmospheric conditions of the plasma applicator 30. The measurements aretransmitted to the controller 224, which determines operating parametersof the generator 14 based on the measurements. If the plasma applicator30 is detected to be contacting tissue, the controller 224 may output anerror signal, indicating that the plasma applicator 30 may need to berepositioned to avoid contact. Once the controller 224 determines thatthe plasma applicator 30 is separated by a sufficient distance, thecontroller 224 adjusts resistivity of the switching element 9 and/oractivates the switching element 9 depending on the configuration of theswitching element 9 and the combined return lead 8. In embodiments wherethe corona electrode 48 is connected via a switch (not shown) instead ofthe switching element 9, then the switch is actuated by the controller224.

After the distance and resistance are set and/or determined by thecontroller 224 to be within prescribed operating parameters, thecontroller 224 signals the generator 14 to output energy to igniteplasma. The controller 224 calculates the initial energy output in viewof the atmospheric conditions, distance, and resistance. In embodimentswhere resistivity is adjustable, resistivity of the switching element 9may also be calculated by the controller 224. Thereafter, the generator14 outputs energy based on these calculations.

After plasma has been ignited at the plasma applicator 30, thecontroller 224 deactivates the switching element 9 and/or adjusts theresistivity thereof to a desired level to maintain the plasma.Additionally, the controller 224 may also utilize the measurements fromthe proximity sensor 60 and the atmospheric sensor 62 after the plasmahas been ignited to make adjustments to the output of the generator 14.

Although the illustrative embodiments of the present disclosure havebeen described herein with reference to the accompanying drawings, it isto be understood that the disclosure is not limited to those preciseembodiments, and that various other changes and modifications may beeffected therein by one skilled in the art without departing from thescope or spirit of the disclosure. In particular, as discussed abovethis allows the tailoring of the relative populations of plasma speciesto meet needs for the specific process desired on the workpiece surfaceor in the volume of the reactive plasma.

What is claimed is:
 1. A plasma instrument comprising: an elongated bodydefining a lumen therethrough, the lumen being in fluid communicationwith an ionizable media source; a plasma applicator coupled to a distalportion of the elongated body, the plasma applicator including: anactive electrode configured to couple to an active terminal of agenerator; and a corona electrode configured to couple to a returnterminal of a generator; and a switching element coupled to the coronaelectrode, the switching element configured to switch between a firststate and a second state, wherein during the first state and the secondstate the corona electrode is electrically coupled to a generator. 2.The plasma instrument according to claim 1, further comprising aproximity sensor configured to measure a distance between the plasmaapplicator and tissue.
 3. The plasma instrument according to claim 1,further comprising an atmospheric sensor configured to measure aproperty of air surrounding the plasma applicator.
 4. The plasmainstrument according to claim 1, wherein the plasma applicator furtherincludes a nozzle coupled to a distal portion of the corona electrode.5. The plasma instrument according to claim 4, wherein the activeelectrode extends through the corona electrode and at least partiallythrough the nozzle.
 6. The plasma instrument according to claim 1,wherein the elongated body is flexible.
 7. A plasma system comprising: agenerator including: an active terminal; a return terminal; and acontroller; an ionizable media source; a plasma instrument including: anelongated body defining a lumen therethrough, the lumen being in fluidcommunication with the ionizable media source; a plasma applicatorcoupled to a distal portion of the elongated body, the plasma applicatorincluding: an active electrode coupled to the active terminal of thegenerator; and a corona electrode configured to couple to a returnterminal of a generator; and a switching element coupled to the coronaelectrode, the switching element-configured to switch between a firststate and a second state, wherein during the first state and the secondstate the corona electrode is electrically coupled to the generator. 8.The plasma system according to claim 7, further comprising a returnelectrode pad coupled to the return terminal.
 9. The plasma systemaccording to claim 8, further comprising: a first return lead coupled tothe corona electrode; a second return lead coupled to the returnelectrode pad; and a common return lead coupled to the first and secondreturn leads, the common return lead being coupled to the returnterminal.
 10. The plasma system according to claim 7, wherein the plasmainstrument further includes a proximity sensor configured to measure adistance between the plasma applicator and tissue.
 11. The plasma systemaccording to claim 10, wherein the controller is further configured tocontrol at least one of energy output of the generator or a state of theswitching element based on the distance.
 12. The plasma system accordingto claim 7, wherein the plasma instrument further includes anatmospheric sensor configured to measure an air property surrounding theplasma applicator.
 13. The plasma system according to claim 12, whereinthe controller is further configured to control at least one of energyoutput of the generator or a state of the switching element based on theair property.
 14. The plasma system according to claim 12, wherein theair property is selected from the group consisting of humidity andoxygen saturation.
 15. The plasma system according to claim 7, whereinthe plasma applicator further includes a nozzle coupled to a distalportion of the corona electrode.
 16. The plasma system according toclaim 15, wherein the active electrode extends through the coronaelectrode and at least partially through the nozzle.
 17. The plasmasystem according to claim 7, wherein the elongated body is flexible.